DISSOCIATIVE/AMNESTIC DRUGS
The drugs in this category include ketamine and scopolamine. These drugs also used to be very popular for labor. Although used less frequently today, they can be very helpful in many situations if given judiciously. They are often combined with other drugs or anesthetic techniques for an excellent overall outcome.

As the category name implies, these drugs cause amnesia which again may not be desired by the mother. In addition, these drugs cause what is know as a dissociative state - what used to be called "twilight sleep". In these situations, the patient appears awake and may even have open eyes, but is "dissociated" from the surrounding environment and gives the appearance of not caring or responding to external stimuli.

Of the two drugs mentioned, scopolamine is not utilized much anymore. This drug causes amnesia and dissociation but does not provide analgesia. Ketamine, on the other hand, provides excellent pain relief and is extremely potent, allowing use of small doses. The most common side effect of ketamine is that it can promote hallucinations and dysphoria (a feeling of unease) - and this limits its usage in some cases. These effects are not surprising since the drug is structurally related to PCP.

NEUROLEPTANALGESIA
The use of these drugs is extremely infrequent today for the purpose of labor analgesia. The most commonly known of this category is Droperidol. This drug is often used in very small doses for treatment of nausea and in this capacity it is very effective. In larger doses, the drug can provide sedation and a state known as neuroleptanalgesia. Droperidol is often combined with a narcotic called Fentanyl (in a commercially available pre-mixed solution called Innovar). The state produced is characterized by a trance-like state with an outwardly tranquil patient in a dissociated state (as explained above, often appearing indifferent to the surroundings).

The most common side effects of droperidol are a drop in blood pressure and depression of respirations. The use of Innovar is not associated with as much respiratory depression as droperidol alone or fentanyl used alone. Droperidol can also produce some feelings of dysphoria when utilized in higher doses.

ANTAGONISTS
Antagonist drugs are used to reverse the action of another drug. I will not discuss much about these here other than to mention that antagonist drugs exist for narcotics (Narcan is the trade name) and for benzodiazepines such as Versed (Romazicon is the trade name of this drug).

These drugs are often utilized when the effect of a previously administered drug should be terminated - either to prevent complications, treat side effects, or because the reason for giving that drug is no longer present (for example, labor pain).

In addition, Narcan is often given to newly delivered babies of mothers who have received intravenous narcotics. This is because the narcotic has crossed the placenta and reached the baby's bloodstream during labor. Giving the newly delivered child Narcan will help the baby be more awake, more arousable, and able to breathe more vigorously.

CONCLUSION
It is clear that effective alternatives for regional techniques in the treatment of labor pain do exist. The medications presented here cause dose-dependent side effects in the mother. In addition, systemic medications such as the ones discussed do cross the placenta and therefore are associated with dose dependent effects in the fetus as well. With careful administration, they can significantly improve comfort and satisfaction for laboring patients.

In part two of this article, I cover the topic of narcotics in much greater detail. These are by far the most commonly used of the intravenous agents and also the most effective.